Combustion engine



Dec. 24,, 1935. w. HARPER, J-R

COMBUSTION ENGINE Filed D80. 8, 1952 2 Sheets-Sheet l CONNECTED TO SOURCE OF' TIMED INTERRUPTED CURRENT TicTl- INVENTOR WILLIAM HARPER, JR.

ATTORNEY De.'24,1935. WHARPERJR 2,025,202

I COMBUSTION ENGINE Filed Dec. 8, 1952 2 Sheets-Sheet 2 T 1 INVENTOR WILLIAM HARPER, JR.

' ATTORNEY Patented Dec. 24, 1935 FATE @FFICE COLEUS'EION ENGINE William Harper, .l'n, Port Washington, N. Y... assignor to. H. B. Motor Eorporation, a corporation of New York Application December 8, 1932, Serial No. 646,224;

6 Claims.

This invention relates to combustion engines and is a continuation in part of my application Serial No. 509,947, filed January 20, 1931.

The object of this invention is to provide an improved ignition system whereby to increase the power output and general overall efificien'cy of combustion engines, and particularly high speed engines wherein such high temperatures are developed as to produce troubles both from fouling of the spark plugs and impairment of the designed spark plug insulation. Ordinary spark plugs retain their designed insulation and capacity for conducting away the heat without fusing the porcelain or other type of insulation used up to and beyond moderate high speeds. When very high speeds are used, as is the tendency in modern combustion engine development, the period between explosions is so short that ordinary plugs readily become overheated, and thereby tend to lose their insulation and may even fuse, as well as crack the fuel and foul by the deposited carbon. To meet this'condition plugs are obtainable on the market which have a good heat conducting capacity, but at the expense of high insulating quality, and also plugs have been developed having a very high insulating quality but at the expense of heat conducting capacity.

According to this invention, an ignition system is provided wherein the advantages of both types of plugs can be effectively utilized and also a multiple plug system is provided wherein one plug is sealedso as to be protected against excessive radiant heat, and such plug may 'prefer-= ably be the high insulation, less heat conducting type. By the cooperation of two plugs so arranged, at least one plug will always fire and thereby prevent the other plug from becoming fouled, and both plugs will thus maintain their insulation and resist the heat at the very highest heats possible to be developed under modern high speed conditions.

Thus, for example, in a two-cycle engine, twice as much heat will be developed in a. given time than in an equal time and number of revolutions by a four-cycle engine. Consequently, if the speed and performance of two-cycle engines in particular are to be improved, ignition at such high speeds and under such intense heats becomes a major problem. In said application above mentioned is disclosed a two-cycle engine capable of very high speed, which cannot be attained by conventional ignition systems heretofore used, which fail either because of breaking down of spark plug so as to obtain higher speeds, this ignition problem becomes more manifest, and dimculty has already been experienced with ignition because of failures from these causes in automobile engines now on the market.

By this invention, the foregoing dimcultiesare avoided and thus high speeds and greater emciency rendered possible by means of spark plugs now available, the exposed plug being thus preferably of the type capable of conducting away 10 the heat as fast as it is formed without fouling or short circuiting, and the other plug in consequence of being shielded from the radiant heat, being capable of having high insulating qualities.

The invention will be more fully understood in 15 connection with the accompanying drawings wherein:

Fig. 1 is a diagrammatic view illustrating the invention as embodied in a two-cycle opposed horizontal cylinder engine;

Fig. 2 is a longitudinal section through one cylinder of such an engine;

Fig. 3 is a detail sectional view showing a modified form of shielded spark plug;

Fig. 4 is a sectional view of a vertical cylinder two-cycle engine embodying the invention; and

Fig. 5 is a. sectional view of a four-cycle engine embodying the invention.

The engine illustrated in Figs. 1 and 2 is a twocycle engine of the type disclosed in my said application Serial No. 509,947, having opposed horizontal cylinders 2 and 2' containing pistons such as piston 3 indicated in Fig. 2.

The drawings show only so much of the engine as is necessary to a complete understanding of the present invention. struction and operation are the same for both cylinders, I shall refer particularly to cylinder 2 and associated parts to the left of Fig. 1, while corresponding parts associated with cylinder 2' ,Will be given similar reference numerals with Inasmuch as the conings is a B. G. Hornet No. 4 having a small mica insulator 6, although this particular plug is shown simply for purposes of illustration as any other plug having good heat dissipating properties may be used equally well. Plug 4 has its spark gap bustion chamber.

extending well into the combustion chamber of the cylinder head and is preferably pointed toward the center of the combustion space so that ignition from this plug will spread instantly throughout the entire compressed charge. The walls of the cylinder head may be flared from the recess containing the plug toward the cylinder barrel as shown in Fig. l 'to facilitate spreading of the flame.

Plug 5 is preferably selected for its good insulating properties, the particular plug 5 shown here for purposes of illustration being a Robert Bosch Midget 12 mm. plug having a so-called petticoat porcelain insulator I which is a good high tension insulator. This plug may of course be replaced by any other type of plug having good insulating properties, such as plug 8 provided with an elongated porcelain insulator 9 shown in Fig. 3.

Plug 5 is shielded in a recess I0 having a restricted orifice or passage l2 which may be formed by an overhanging lip on the wall of the cylinder head and which connects recess II) with the com- Passage or orifice I2 is preferably set at such an angle that its entrance is adjacent the water-jacketed wall l3 of the cylinder, this being the region of the combustion chamber where the radiant heat is at a minimum.

Passage or orifice I2 is likewise disposed at such an angle to recess III that the wall of the passage intercepts and absorbs the radiant heat of combustion which enters the passage and thereby described. Ignition from shielded plug 5 will not be as rapid as from exposed plug 4. If plug 4 is 'fouled when the engine is started, then plug 5,

which sparks simultaneously with plug 4, will ignite the charge while warming up the engine until plug 4 has become hot enough to burn off the oil or carbon which has caused the fouling.

scavenging of recess I0 is accomplished automatically due to the position of plug 5 in said recess. After each explosion the pressure in recess l0 drops to the same point as the pressure in the cylinder and most of the exhaust gas flows stroke, the compressed fresh mixture forces theresidual exhaust gas inrecess l0 back to the base of the plug. The points of the spark gap are close enough to passage I2, and the clearance back of the points is sufllcie'nt, to allow such residual exhaust gas to be pushed back away from the points on each compression stroke.

The spark plugs of each pair of opposed cylinders may be connected in series or in parallel and may be functioned by any suitable source of timed interrupted current such as a dual ignition magneto or a battery controlled by a suitable distributor or breaker. In the system of Fig. 1, induction coil 15 has its primary winding connected to any suitable source of timed interrupted current and has two secondary windings l5 and II which are preferably grounded at their midpoints. Winding It has one end connected 'to one or lower shielded spark plug 5 of cylinder 2'. Similarly, winding I! has one end connected to shielded spark plug 5 of cylinder 2 and its other end connected to exposed plug 4' of opposed cylinder 2'. Hence, if one secondary winding 5 should fail, for example if secondary winding l6 should fail for any reason, exposed plug 4 of cylinder 2 and shielded plug 5' of opposed cylinder 2 would be disabled, while shielded plug 5 of cylinder 2 and exposed plug 4' of cylinder 2 would re- 10 main operative. Such continued operation of a shielded plug in one cylinder and an exposed plug in the corresponding opposed cylinder insures more eflicient ignition than failure of two similar plugs and continued operation of the other two 15 similar plugs in opposed cylinders. Also, grounding of the secondary windings at their midpoints further reduces the danger of failure of ignition since, if one plug fails due to any cause such as its terminal connector becoming detached, the 20 other plug connected to the same secondary winding will continue to operate as before. Another advantage of the above ignition system, which obtains regardless of the types of plugs used or their method of connection to the secondary 25 windings of the induction coils, is that the electrical duty is divided up between a plurality of separate coils so that the engine may be operated at very high speeds without encountering the electrical limit of coil saturation frequency.

The vertical two-cycle engine shown in Fig. 4 is of the usual construction having a cylinder l9 which may be water-jacketed or provided with air cooled fins 20, crank case 2| and piston 22 connected to crank shaft 23 by connecting rod 24. 35 The engine is also provided with valved inlet 25, transfer port 26. and exhaust port 21. Spark plugs 4 and. 5 are set in recesses arranged in thehead of the cylinder as previously described, plug 4 being exposed and plug 5 being shielded in a 40 recess 28 having a restricted orifice or passage 29 connecting said recess with the combustion chamber.

The four-cycle engine shown in Fig. 5 is of any suitable construction, having a cylinder 30, 46 piston 3|, inlet valve 32 and exhaust valve 33. Spark plugs 4 and 5 are mounted as previously described, the latter being shielded in a suitable vrecess 34 having a restricted orifice or passage 35 connecting said recess with the combustion 60 chamber.

Although no one spark plug has yet been designed to combine the advantages of good electrical insulation and good heat dissipation, these advantages are effectively combined in the two 55 or more plugs described above. I do not limit myself to two spark plugs in a cylinder as I may employ a plurality of exposed plugs and a plurality of shieldedplugs in one cylinder, or in some cases may use a single plug of one type and a plurality of plugs of another type in one cylinder connected either in series or in parallel and operated in any suitable manner. Existing typesof engines having removable cylinder heads may have such heads removed and replaced by cylinder heads of my improved construction. Many variations in the arrangement'and mode of operation of the spark plugs and the ignition system as a whole will readily occur to those skilled in the art with- 70 out departing from the scope and spirit of the appended claims.

The invention claimed is:

1. An ignition system for combustion engines comprising a plurality of spark plugs having' relatively high insulating properties and relatively low heat dissipating properties and a plurality of spark plugs having rapid heat dissipating properties and relatively low insulating properties, a source of interrupted current, and a plurality of independent energizing circuits electrically connected to said source of current and each connected to at least one spark plug having relatively high insulating properties and at least one spark plug having rapid heat dissipating properties.

2. An ignition system for combustion engines comprising a plurality of spark plugs having relatively high insulating properties and relatively low heat dissipating properties and a plurality of spark plugs having rapid heat dissipating properties, a source of interrupted current, and an induction coil having a primary winding connected to said source of current and a plurality of secondary windings each connected to at least one spark plug having relatively high insulating properties and at least one spark plug having rapid heat dissipating properties.

3. An ignition system for combustion engines comprising a plurality of spark plugs having relatively high insulating properties and relatively low heat dissipating properties and a plurality of spark plugs having rapid heat dissipating properties, a source of interrupted current, and an induction coil having a primary winding connected to said source or current and a plurality oi! secondary windings grounded at their midpoints and each having one end connected to a spark plug having relatively high insulating properties and other cylinder.

the other end connected to a spark plug having rapid heat dissipating properties.

4. A combustion engine comprising opposed cylinders each containing a spark plug having relatively high insulating properties and relatively for rapid heat dissipation exposed to the radiant 15 heat of combustion, a source of interrupted current, and a plurality of energizing circuits electrically connected to said source of current and each connected to the high tension insulated spark plug of one cylinder and the rapid heat dissipating 2o spark plug of the other cylinder.

6. A combustion engine comprising opposed cylinders each containing a spark plug having a high tension insulator shielded from the radiant heat of combustion and a second spark plug adapted for rapid heat dissipation exposed to the radiant heat of combustion, a source of interrupted current, and an induction coil having a primary winding connected to said source of current and a pair of secondary windings each connected to the 0 high tension insulated spark plug of one cylinder and the rapid heat dissipating spark plug of the WILLIAM HARPER, JR. 

